This invention relates to an iron-base amorphous alloy that has excellent corrosion resistance, and can be readily pulverized for use in such form. Amorphous alloys are typically formed by rapid solidification of the molten metal alloy and are characterized by the absence of any crystalline structure, the conventional structure, i.e. orderly arrangement of atoms, found in ingot cast alloys.
Amorphous alloys have been known for years, particularly in the last decade. A recent development for an iron-base amorphous alloy is taught by Masumoto et al. in U.S. Pat. No. 3,986,867. These alloys contain 1-40 atom percent chromium, 7-35 atom percent of at least one of the metalloids phosphorus, carbon and boron, balance iron, and optionally, also contain less than 40 atom percent of at least one of nickel and cobalt, less than 20 atom percent of at least one of molybdenum, zirconium, titanium and manganese, and less than 10 atom percent of at least one of vanadium, niobium, tungsten, tantalum and copper.
The Masumoto et al alloys are said to provide good mechanical resistance and corrosion resistance. Such alloys are suitable for structural reinforcement members, such as in tires, for example.
A still more recent entry into the field of iron-base amorphous alloys is disclosed by the patent to Kavesh et al in U.S. Pat. No. 4,260,416. These alloys are defined by the composition Fe.sub.a Cr.sub.b C.sub.c P.sub.d Mo.sub.e W.sub.f Cu.sub.g B.sub.h Si.sub.i, where "a" ranges from about 61-75 atom percent, "b" ranges from about 6-10 atom percent, "c" ranges from about 11-16 atom percent, "d" ranges from about 4-10 atom percent, "e" ranges from about 0-4 atom percent, "f" ranges from about 0-0.5 atom percent, "g" ranges from about 0-1 atom percent, "h" ranges from about 0-4 atom percent and "i" ranges from about 0-2 atom percent, with the proviso that the sum [c+d+h+i] ranges from 19-24 atom percent and the fraction [c/(c+d+h+i] is less than about 0.84. The alloy is characterized as being strong, ductile, and resistant to corrosion and thermal embrittlement.
For further reference, additional iron-base amorphous alloy are disclosed in the several patents to DeCristofaro et al, namely, U.S. Pat. Nos. 4,249,969 and 4,219,355, and European Patent Application No. 26863.
It is evident from the above described amorphous alloys that the respective alloy system can be complex and thereby present problems in the production of the alloy and its usefulness thereafter. The alloy of the present invention presents a less complex alloy system, while yielding an alloy having excellent corrosion resistance and a low ductility. This combination of properties, to be discussed hereafter in detail, renders the resulting product ideally suited to pulverization and as a filler for paints, plastics, etc.